Leads implanted in or about the heart have been used to reverse certain life threatening arrhythmia, or to stimulate contraction of the heart. Electrical energy is applied to the heart via the leads to return the heart to normal rhythm. Leads have also been used to sense in the atrium or ventricle of the heart and to deliver pacing and defibrillation pulses to the atrium or ventricle.
Permanent transvenous pacing is performed using a lead positioned within one or more chambers of the heart. One or more leads may be positioned in the ventricle or in the atrium through a subclavian vein, and the lead terminal pins are attached to a pacemaker which is implanted subcutaneously. One approach to heart pacing is to place an electrode in the apex of the right ventricle. The lead is held in place either passively or actively using a helix, for example.
Another approach is to place the electrode against the high ventricular septum or outflow tract. However, current leads require a lead placed with the electrode in such a position to be actively fixated. This possibly may result in trauma to the heart from cyclical heart motion, micro-dislodgement, and relatively higher pacing thresholds.